This invention relates to grinding apparatus and particularly though not exclusively to apparatus for the grinding of the ends of helical springs.
Heretofore it has been customary to sandwich grind, i.e. grind the opposed ends of a helical spring or other workpiece simultaneously, by passing the spring between two spaced, co-axial, rotating abrasive wheels. For this purpose the spring is held in a rotary magazine and is traversed about an axis lying parallel with the abrasive wheel axis into and out of the space between the two abrasive wheels, the axis of the spring also being parallel with the aforementioned axes. The material is ground from the ends of the spring progressively by reducing the spacing between the abrasive wheels. This type of arrangement has certain disadvantages. If production rates are to be maximised it is necessary for the material removal rate by the abrasive wheels to be high. In consequence, considerable heat is generated which can alter the temper and mechanical qualities of the springs. In addition the abrasive wheels are subject to considerable wear, and require frequent dressing, for example every half hour, involving machine `down-time` and subsequent machine resetting in order to produce springs of predetermined dimensions. Replacement of excessively worn abrasive wheels is also a time consuming and therefore costly operation in terms of lost production.